Shanghai will intensify efforts to improve the city's air quality as its mayor vowed on Wednesday to lower the annual average concentration of PM2.5 by at least 20 percent by 2017.

While promoting its transformation and development, Shanghai will also insist on improving the city's ecological environment, Jiefang Daily quoted Mayor Yang Xiong as saying.

Yang said the city will strengthen efforts to improve water and air quality, especially PM2.5, fine particles only 2.5 micrometers in size, based on the clean-air plan that was released recently.